Internationally, he was best known for his role in Bong Joon-ho's Academy Award–winning film Parasite (2019), for which he won a Screen Actors Guild Award along with his castmates.

The dramas Coffee Prince and Behind the White Tower (both 2007) brought Lee mainstream popularity, which he followed with Pasta (2010), Golden Time (2012) and My Mister (2018).

[5] Lee eventually achieved his breakthrough in 2007 with the critically lauded medical drama White Tower and the highly popular romantic series Coffee Prince.

[7] Besides Coffee Prince, he worked with director Lee Yoon-jung two other times—in the sports-themed Taereung National Village in 2005, and in the slice-of-life drama Triple in 2009.

He appeared in films directed by Hong Sang-soo, such Night and Day, Lost in the Mountains, Oki's Movie, Nobody's Daughter Haewon and Our Sunhi.

[8] Lee also headlined Paju,[11] for which he won the Best Actor award at the Las Palmas de Gran Canaria International Film Festival held in Spain.

[14][15][16] Petty Romance reunited him with his My Sweet Seoul co-star Choi Kang-hee,[17][18][19] and one-upmanship action comedy Officer of the Year (also known as Arrest King) soon followed.

He continually defended the importance of the short drama format as a training ground for young talent, acknowledging its contribution to his own career.

Parasite was directed by Bong Joon-ho and became the first South Korean film to win the Palme d'Or as well as the Academy Award for Best Picture.

As the drama series debut of renowned filmmaker Kim Jee-woon, the sci-fi thriller is based on the Korean webtoon of the same name.

[54] As a result, he voluntarily dropped out of No Way Out, an upcoming thriller drama serial which just started its production days before the revelation of his alleged drug use.

[64] Korean opposition party questioned the coverage of Lee's suspected drug use, stating that it took away public's attention from unfavorable developments involving the government and ruling People Power Party which member and Justice Minister Han Dong-hoon commented that "the drug use issue was unrelated to politics".

[67][68][69] The police earlier received a report from his wife that Lee had left home after "writing a memo akin to a suicide note".

Director Bong Joon-ho and other prominent figures demanded an inquiry into the role of South Korean media and police in Lee's death.